Method and apparatus for maintaining cooling of modular electronic system during module removal

ABSTRACT

In one embodiment, a method includes receiving an indication at a modular electronic system of initiation of online removal for a module removably inserted into a slot of the modular electronic system, increasing a fan speed at the modular electronic system before the module is removed, monitoring an internal temperature at the modular electronic system, and providing an indication that the module is ready for removal upon reaching a specified cooling state at the modular electronic system based on the temperature monitoring. A panel on an adjacent module is opened and extends into the slot upon removal of the module to substantially block airflow bypass from the slot and maintain cooling within the modular electronic system. An apparatus and logic are also disclosed herein.

TECHNICAL FIELD

The present disclosure relates generally to modular electronic systems,and more particularly, maintaining cooling of modular electronic systemsduring module replacement.

BACKGROUND

Modular electronic systems are designed to provide flexibility toconfigure systems as per user needs. These systems typically havemultiple slots to accommodate a variety of modules (e.g., line cards,service cards, fabric cards, and the like). Most of these modules can bereplaced with the latest product upgrades without disturbing normaloperation of the system (i.e., hot swappable). It is desirable toreplace faulty modules without powering down the system or impacting theperformance of other modules in the system, such as by disrupting systemcooling.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a perspective partial view of an example of a modularelectronic system.

FIG. 1B is a front schematic view of the modular electronic system ofFIG. 1A.

FIG. 2 is a front schematic view of the modular electronic system ofFIG. 1B with a module removed.

FIG. 3 is a block diagram depicting an example of a network device thatmay be used to implement the embodiments described herein.

FIG. 4 is a flowchart illustrating an overview of a process formaintaining cooling of the modular electronic system during removal of amodule, in accordance with one embodiment.

FIG. 5 is a flowchart illustrating details of the process of FIG. 4, inaccordance with one embodiment.

FIG. 6 is a schematic top view of a module with airflow panels in aclosed position, in accordance with one embodiment.

FIG. 7 is a schematic top view of the module of FIG. 6 with one of theairflow panels in an open position.

FIG. 8 is a perspective of the airflow panel of FIG. 6, in accordancewith one embodiment.

FIG. 9 is a schematic top view of a servo motor operated airflow panel,in accordance with one embodiment.

FIG. 10 is a schematic top view of a shape memory alloy filamentoperated airflow panel, in accordance with one embodiment.

FIG. 11 is a graph illustrating an example of impacted moduletemperature when a module is removed without a waiting period.

FIG. 12 is a graph illustrating an example of impacted moduletemperature when a module is removed after a waiting period.

FIG. 13 is a graph illustrating an example of impacted moduletemperature with an airflow panel deployed.

Corresponding reference characters indicate corresponding partsthroughout the several views of the drawings.

DESCRIPTION OF EXAMPLE EMBODIMENTS Overview

In one embodiment, a method generally comprises receiving an indicationat a modular electronic system of initiation of online removal for amodule removably inserted into a slot of the modular electronic system,increasing a fan speed at the modular electronic system before themodule is removed, monitoring an internal temperature at the modularelectronic system, and providing an indication that the module is readyfor removal upon reaching a specified cooling state at the modularelectronic system based on the temperature monitoring. A panel on anadjacent module is opened and extends into the slot upon removal of themodule to substantially block airflow bypass from the slot and maintaincooling within the modular electronic system.

In another embodiment, an apparatus generally comprises a framesupporting a plurality of slidably removable modules, at least a portionof the modules each comprising a panel movable between a closed positionand an open position in which the panel extends into an open slot fromwhich a module is removed, a cooling fan for cooling said modules, athermal sensor for sensing an internal temperature at the apparatus, anda processor configured to receive an indication of an online removalprocess for the module, increase a speed of the cooling fan, and providean indication that the module is ready for removal upon identifying thatthe internal temperature has reached a cooling state. The panel on anadjacent module is configured to open and extend into the slot uponremoval of the module to substantially block airflow bypass from theslot and maintain cooling within the modular electronic system.

In yet another embodiment, logic is encoded on one or morenon-transitory computer readable media for execution and when executedby a processor operable to identify initiation of an online removalprocess for a module removably inserted into a slot of a modularelectronic system, increase a fan speed at the modular electronic systembefore the module is removed, monitor an internal temperature at themodular electronic system, provide an indication that the module isready for removal upon reaching a specified cooling state at the modularelectronic system based on said monitored temperature, and unlock apanel on an adjacent module so that the panel is free to open and extendinto the slot upon removal of the module to substantially block airflowbypass from the slot and maintain cooling within the modular electronicsystem.

Example Embodiments

The following description is presented to enable one of ordinary skillin the art to make and use the embodiments. Descriptions of specificembodiments and applications are provided only as examples, and variousmodifications will be readily apparent to those skilled in the art. Thegeneral principles described herein may be applied to other applicationswithout departing from the scope of the embodiments. Thus, theembodiments are not to be limited to those shown, but are to be accordedthe widest scope consistent with the principles and features describedherein. For purpose of clarity, details relating to technical materialthat is known in the technical fields related to the embodiments havenot been described in detail.

Network devices such as switches, routers, server racks, or otherelectronic devices may be configured as a modular electronic system witha plurality of removable modules (e.g., service cards, line cards,fabric cards, or other cards, components, or modules). In a modularconfiguration system, Online Insertion & Removal (OIR) refers to aprocess of replacing a module for repair or replacement (e.g., productupgrade, failed module replacement) without disrupting the performanceof the modular system. During this process, the system continues to befunctional and a faulty module is replaced with a new or repairedmodule.

In an air-cooled modular electronic system, cooling air is supplied toeach of the modules to maintain a normal cool state of each module. Whena module is removed from the system, a large amount of cooling air flowsinto a space (slot) from which the module has been removed and thecooling balance among the remaining modules is impacted. The open slotcauses the system airflow to be unbalanced as the empty space provides apath of least resistance and airflow is allowed to bypass through thisspace resulting in other areas or components failing to receivesufficient airflow for cooling.

Depending on the complexity of the system design, the OIR process maytake some time, during which the module slot would remain open toambient air rushing in the now open slot. In a fan cooled system that isoptimized for uniform flow through each of the slots, airflow would benegatively impacted as the slot opening would offer the least resistanceairflow path and most of the air would start flowing through that openslot. This would reduce the airflow for other modules, thereby causingtheir component temperatures to rise, which often leads to overheating,and may potentially result in shorter life span or catastrophic failureof one or more of the operational modules remaining in the system.

In one example, it is desired to extend the OIR process to at least fiveminutes. This means that the open slot could be allowing air inrush forup to five minutes, starving air flow from the other cards, and possiblycausing system failure. Meeting five minutes OIR times with hardwarecomponents operating above 80 Watts, for example, is increasinglydifficult, if not impossible with conventional systems typically onlyallowing for replacement times of two minutes or less before overheatingoccurs.

The embodiments described herein provide for maintaining of cooling ofmodular electronic systems during module removal. As described in detailbelow, one or more embodiments provide cooling logic and an airflowpanel to prevent the loss of cooling to modular components when modulesare removed. In one or more embodiments, cooling fan logic may be usedto increase cooling prior to removal of an OIR module to prevent theloss of cooling to the active modules during OIR. In one or moreembodiments, in order to avoid airflow bypass from the open slot, apanel (airflow panel, flap, door) is provided, which is operationalduring OIR conditions and configured to prevent airflow bypass duringmodule OIR. One or more embodiments may improve the OIR time limit foran extended period of time and possibly indefinitely, thereby providinghigh reliability and availability of modular electronic systems.

The embodiments described herein may operate in the context of a datacommunications network including multiple network devices. The networkmay include any number of network devices in communication via anynumber of nodes (e.g., routers, switches, gateways, controllers, edgedevices, access devices, aggregation devices, core nodes, intermediatenodes, or other network devices), which facilitate passage of datawithin the network. One or more of the network devices may comprise amodular electronic system as described herein. The network devices maycommunicate over one or more networks (e.g., local area network (LAN),metropolitan area network (MAN), wide area network (WAN), virtualprivate network (VPN) (e.g., Ethernet virtual private network (EVPN),layer 2 virtual private network (L2VPN)), virtual local area network(VLAN), wireless network, enterprise network, corporate network, datacenter, Internet, intranet, radio access network, public switchednetwork, or any other network).

Referring now to the drawings, and first to FIGS. 1A and 1B, aperspective and front view, respectively, of one example of a modularelectronic system 10 is shown. The modular electronic system 10 mayoperate, for example, as a switch, router, server, or any other networkdevice comprising modules (components, cards, trays, elements) includedin modular sections.

The modular electronic system 10 shown in FIGS. 1A and 1B comprises aplurality of components positioned horizontally or vertically in asystem frame 9. The system 10 may include one or more frames orstructures 9 configured to support the components and slidably receiveany number of removable modules. Most or all of the components maycomprise modules that are slidably removable from the frame. The exampleshown in FIGS. 1A and 1B includes power components 11, air outlet 12,air inlet 13, fan trays 15, fiber management 14, and a plurality ofcards 16 (e.g., fabric cards, line cards, service cards, combo cards). Acard cage gap 17 is interposed between the two rows of cards 16. It isto be understood that the type, number, and arrangement of componentsand modules shown in FIGS. 1A and 1B is only an example and theelectronic modular system may include any number or type of modulesarranged in any format.

One or more removable modules 16 comprise an OIR button 19 a used inremoval of the module 16. As described in detail below, the OIR buttons19 a may be in communication (e.g., mechanically, electronically, orboth) with cooling logic 18 a to initiate increased cooling of themodules 16 prior to removal of the OIR module, and with panel logic 18 bto unlock an airflow panel on a module adjacent to the module to beremoved to prevent airflow bypass once the module is removed.

The term OIR or online removal as used herein refers to removal of amodule from the modular electronic system without removing power fromthe system (i.e., one or more remaining modules are operational). Themodule 16 removed from the system for replacement, repair, or upgrade isreferred to herein as the “OIR module”. The module 16 (or modules) thatare thermally impacted due to airflow bypass from the open slot left bythe OIR module is referred to herein as the “impacted module”.

In one or more embodiments, an indication may be provided to notify auser when it is acceptable to remove the OIR module after initiation ofthe online removal process. For example, the modular electronic systemmay comprise a display or light on the chassis itself or each module. Inthe example shown in FIGS. 1A and 1B, the removable modules 16 comprisean OIR indicator 19 b, which may comprise, for example, an LED (LightEmitting Diode) or other light or element operable to indicate thestatus of the OIR module. In one example, an LED may flash, light up, orchange color to indicate that the module is ready to be removed. The OIRindicator 19 b may, for example, be turned off under normal operatingconditions and turned on to indicate the status of the OIR module priorto removal (e.g., after initiation of the OIR process by pressing OIRbutton 19 a) and after replacement of the module until normal operatingconditions are reached. For example, once the OIR button 19 a on the OIRmodule is pressed, the LED 19 b may turn amber, blinking blue, or anyother color to indicate that the OIR module is not ready to be removed,and then turn green, solid blue, or any other color indicating that theOIR module can be safely removed once the system (e.g., one or moremodules) has reached a specified cooling state (e.g., specifiedtemperature or stabilized temperature). In one embodiment, a label maybe provided on the module or system for use in interpreting theindicator 19 b.

As described below, a fan speed may be increased once the OIR button 19a is pressed. One or more internal thermal sensors 18 c in the modularelectronic system 10 may be monitored to determine when the internaltemperature has stabilized or reached a specified temperature, forexample. When this cooling state is reached, the OIR indicator 19 b maychange color to indicate that the OIR module can be safely removed. Oncethe OIR module is removed, an airflow panel located on a module adjacentto the OIR module may be deployed to prevent airflow bypass through theopen slot, as described below with respect to FIG. 2.

In the example shown in FIG. 1B, the FC2-S2 card (OIR module) is to beremoved for replacement or upgrade. In this example, the FC6-S2 card maybe referred to as the impacted module since it would be thermallyimpacted if airflow was allowed to bypass from the open slot once theOIR module is removed.

In order to start the OIR process, maintenance personnel may select theOIR button 19 a (e.g., button mechanically depressed, tab pressed, levermoved or mechanically engaged, or other input at a selectable interface)on the module to be removed (FC2-S2 card in the example of FIG. 1B).This signals the cooling logic 18 a to increase the fan speed to furthercool the modules 16. As described in detail below, one or more thermalsensors 18 c located on or near the modules 16 are monitored todetermine when the temperature has stabilized to its lowest point. TheOIR indicator 19 b may signal that the OIR module is not ready forremoval when the OIR button 19 a is first pressed. Once the temperaturehas stabilized (as indicated by one or more thermal sensors 18 c), theOIR indicator 19 b changes state to indicate that the OIR module 16 isready for removal.

In one or more embodiments, the modules 16 may be physically locked inplaced (e.g., ejector locked) until the temperature has stabilized afterthe fan speed has increased. Once the modules are sufficiently cooled,the OIR module may be physically unlocked or released (e.g., ejectorunlocked) at approximately the same time (or slightly before) the OIRindicator 19 b changes state to indicate that the OIR module is readyfor removal.

FIG. 2 illustrates the modular electronic system shown in FIG. 1B withone of the modules (FC2-S2 card) removed. As shown in FIG. 2, an airflowpanel 20 is deployed into opening 22 when the OIR module is removed toprevent airflow bypass through the open slot by limiting or restrictingthe flow of cooling air through the slot.

As described in detail below, after the OIR process is initiated, theairflow panel 20 may be unlocked by panel logic 18 b so that it is readyto deploy into the open slot when the OIR module is removed (FIGS. 1Band 2). The panel logic 18 may initiate the unlocking or releasing ofthe airflow panel 20 on one of the adjacent modules (e.g., FC1-S2 cardor FC3-S2 card) after initiation of the OIR process. The panel 20 may beunlocked as soon as the OIR button 19 a is pressed or after thestabilized temperature is reached and the OIR module is ready to beremoved.

It is to be understood that the modular electronic system 10, modules16, OIR button 19 a, and OIR indicator 19 b shown in FIGS. 1A, 1B, and 2and described above are only examples, and that a different number,type, or arrangement of modules, components, or OIR mechanisms may beused without departing from the scope of the embodiments.

FIG. 3 illustrates an example of a network device (modular electronicsystem) 30 that may be used to implement the embodiments describedherein. In one embodiment, the network device 30 is a programmablemachine that may be implemented in hardware, software, or anycombination thereof. The network device 30 includes one or moreprocessor 32, memory 34, network interfaces 36, and cooling/panel logicelement 38.

Memory 34 may be a volatile memory or non-volatile storage, which storesvarious applications, operating systems, modules, and data for executionand use by the processor 32. For example, components of thecooling/panel element 38 (e.g., code, logic, software, firmware, etc.)may be stored in the memory 34. The network device 30 may include anynumber of memory components.

Logic may be encoded in one or more tangible media for execution by theprocessor 32. For example, the processor 32 may execute codes stored ina computer-readable medium such as memory 34. The computer-readablemedium may be, for example, electronic (e.g., RAM (random accessmemory), ROM (read-only memory), EPROM (erasable programmable read-onlymemory)), magnetic, optical (e.g., CD, DVD), electromagnetic,semiconductor technology, or any other suitable medium. In one example,the computer-readable medium comprises a non-transitorycomputer-readable medium. The processor 32 may be operable to performone or more steps shown in the flowcharts of FIG. 4 or 5, for example.The network device 30 may include any number of processors 32.

The cooling/panel logic 38 may comprise one or more components(software, code, logic) operable to monitor module presence, receiveinput from OIR button 19 a, receive input from thermal sensors 18 c,control fan speed based on ambient temperature sensor and thermal sensorof critical modules 16, activate unlocking of panel 20, and lock/unlockmodule ejectors (FIGS. 2 and 3).

The network interfaces 36 may comprise any number of interfaces(connectors, line cards, ports) for receiving data or transmitting datato other devices. The network interface 36 may include, for example, anEthernet interface located on one of the modules 16 for connection to acomputer or network.

It is to be understood that the network device 30 shown in FIG. 3 anddescribed above is only an example and that different configurations ofnetwork devices may be used. For example, the network device 30 mayfurther include any suitable combination of hardware, software,algorithms, processors, devices, components, or elements operable tofacilitate the capabilities described herein.

FIG. 4 is a flowchart illustrating an overview of a process formaintaining cooling in the modular electronic system 10 upon removal ofone of the modules 16, in accordance with one embodiment. At step 40,the system receives an indication of initiation of an online removalprocess for a module 16 inserted into a slot 22 of the modularelectronic system 10 (FIGS. 2 and 4). The indication may be based, forexample, on maintenance personal pressing the OIR button 19 a on themodule 16 to be removed. This may initiate one or more actions,including, for example, increasing of the fan speed at one or morecooling fans (e.g., at fan tray 15) at the modular electronic system 10to reduce the temperature of the modules 16 (step 41). This may alsoresult in the locking of the OIR module 16 in place (if the module isnot already locked) and signaling of an indication that the module isnot ready for removal (e.g., LED turning on, changing color, blinking).One or more temperature sensors 18 c internal to the modular electronicsystem 10 (e.g., one or more temperature sensors in slots 22, adjacentto the slots, or near or on the modules 16) may be monitored todetermine when the temperature reaches a specified cooling state at themodular electronic system 10 (e.g., sensors stabilize to lowesttemperature or reach a threshold temperature) (steps 42 and 43).

When the temperature has stabilized to the specified cooling state, theOIR module 16 is ready to be removed and an indication is provided (step44). An indication that the modular electronic system (e.g., module,portion, or section of modular electronic system) has reached itscooling state may comprise, for example, a visible indication (e.g., achange in color of a light (e.g., LED turning off, changing color, orblinking light turning solid)), or unlocking of a physical lock (e.g.,module ejector unlocked or released). A lock on the airflow panel 20 mayalso be released. The lock may be released at the same time that the LED19 b indicates the OIR module 16 is ready to be removed or may bereleased as soon as the OIR button 19 a is pressed. Once the OIR module16 is removed, the airflow panel on an adjacent module is free to bereleased from the adjacent module and deployed into the open slot 22 toprevent air bypass from the slot and maintain cooling within the modularelectronic system (step 46).

FIG. 5 illustrates details of the process shown in FIG. 4 formaintaining cooling of a modular electronic system during moduleremoval, in accordance with one embodiment. At step 48, the system isoperating normally (i.e., the OIR process has not been initiated). Theejectors on the modules 16 are locked (no OIR buttons 19 a have beenpressed) and the OIR LEDs 19 b on the modules are off (FIGS. 2 and 5).The system ambient temperature is monitored (step 49). In one example,an ambient temperature≤30° C. is preferred. At step 50, the OIR button19 a on one of the modules 16 is pressed. The OIR LED 19 b on the moduleturns on (e.g., turns amber or blinking blue). The ejector is not yetreleased. The fan speed is increased from nominal 50% to 100% (or anyother increase) (step 51). The thermal sensors are monitored todetermine when the sensors stabilize to a lowest temperature (step 52).This time period may be referred to as a “waiting period” or “coolingperiod”.

At step 53, the temperature sensors have stabilized and the OIR LED 19 bon the OIR module 16 changes (e.g., turns green or solid blue light) andthe module ejector is unlocked or released. The lock on airflow panel 20on an adjacent module is also released. The OIR module 16 may then bepulled out thereby releasing the panel on the adjacent module so that itcovers the opening in the slot left behind by the removed OIR module(step 54). The system may then run for an extended period (or possiblyindefinitely). At step 55, a replacement module 16 is inserted into theopen slot 22. The panel 20 is closed and locked in place when thereplacement module is inserted into the slot due to inward movement ofreplacement module (step 56). The module power is turned on and themodule status LED turns green (step 57). The fan speed may be adjustedbased on the ambient temperature (step 58). The system returns to normaloperation, the ejector on the module is locked, and the OIR LED on themodule is turned off (step 59).

It is to be understood that the processes shown in FIGS. 4 and 5, anddescribed above are only examples and that steps may be added, combined,removed, or modified, without departing from the scope of theembodiments.

As previously described with respect to FIG. 2, a panel 20 attached toan adjacent module (e.g., FC3-S2 card) may be deployed into the cavity22 from which the module (e.g., FC2-S2 card) is removed to cover theopen slot left by removal of the module during OIR. In one embodiment,the panel 20 is an integral part of the module 16 and remains within afootprint of current module boundaries. In one or more embodiments, thepanel 20 is controlled between an open position in which the panel isdeployed into the adjacent open slot 22 and a closed (locked) positionin which the panel is generally longitudinally parallel to the moduleand the adjacent module is inserted into the slot. The panel 20 ispreferably designed to prevent obstruction of electronic components andinterference with removal and insertion of adjacent modules 16. Asdescribed below, the panel 20 may be provisioned on one or both sides ofthe module 16 to cover one or both adjacent slots, with each paneloperating independently from one another.

FIG. 6 illustrates one embodiment in which panels 60 are located onopposite sides of the module 61. A panel assembly comprises a fixedportion 62 and the movable panel 60 connected through a hinge joint 64to the fixed portion. The panel assembly may be attached to a face plate63 of the module and utilize the hinge 64 and one or more torsionsprings 65 to manage movement of the panel 60 between the open andclosed positions. One or more protective stand-offs 66 may beincorporated into the module 61 to avoid the panel 60 hitting electroniccomponents 68. As shown in FIG. 6, an edge portion 69 of the panel 60may be angled to avoid scratching adjacent modules during insertion andremoval. Also, the angled edge 69 may be used to prevent interferencewith adjacent modules in case the panel 60 is stuck inwards and themodule needs to be removed. A plastic coating (e.g., frictionlessmaterial) may be applied to the panel 60 to avoid scratches duringsliding movement between modules. The panel 60 may be constructed fromsheet metal, a polycarbonate material, or any other suitable material.

FIG. 7 shows the module of FIG. 6 with one of the panels 60 in an openposition, in which the panel 60 extends generally 90 degrees from alongitudinal axis of the module 61 to prevent airflow bypass in anadjacent open slot when the adjacent module is removed (FIG. 2). Aspreviously noted, the panels 60 may operate independently. For example,panels 60 may be in their closed positions (as shown in FIG. 6), bothpanels may be in their open positions, or one panel may be open whilethe other is closed (as shown in FIG. 7).

FIG. 8 is a perspective of one example of the panel assembly shown inFIGS. 6 and 7. The fixed portion 62 is attached to the module (e.g.,face plate of module as described above) and may be formed from sheetmetal or other suitable material. The panel 60 is connected to the fixedportion 62 through the hinge joint 64 comprising a pin 85 extendingthrough interlocking fingers 86 connected to the panel and 88 connectedto the fixed portion 62. A mechanical arrangement with a small number(e.g., two) of hinge joints allows for controlled and smooth movement ofthe panel 60. As previously noted, the panel 60 may be formed frompolycarbonate, sheet metal, or any other suitable material.

FIG. 9 illustrates an example of a locking mechanism that may be used toretain panel 90 in its closed position. In one or more embodiments, anelectromechanical mechanism may be used to unlock the panel. Aspreviously described the rotatable panel 90 is attached to a fixedportion 92 through hinge 94. A locking pin 98 on hinge lever 93 islocked in place by a spring lever 97, which is held in its lockedposition by torsion spring 99. The hinge lever 93 is attached to thepanel 90 and slides within a slotted bracket 96. In one embodiment, thedesign of the spring lever 97 is such that the pin 98 may be locked inplace through a small force pressing against it (press-fit), and the pinis released when the spring lever 97 is opened, as shown in the cut-outview of the panel 90 in its open position. The panel 90 is spring loadedby torsion spring 95 in its open position and the panel is free to pivotabout hinge joint 94 to its open position once the locking pin 98 isreleased from the spring lever 97. As described below, movement of thepanel 90 towards its closed position upon insertion of the OIR moduleforces the pin 98 back into its locked position.

In one embodiment, a servo motor 100 engages with the spring lever 97 torelease the locking pin 98 from the spring lever. In one example, theminiaturized servo controlled motor 100 may be connected to the springlever 97 to provide rotation needed for the spring lever (held in placeby spring 99) to release locking pin 98. The servo motor 100 providesangular rotation to move the spring lever 97 thereby allowing thelocking pin 98 and connected hinge lever 93 to move along the slottedbracket 96 and open the panel 90 to cover the open slot left by theremoved module in the adjacent slot.

As shown in the cut-out view, the locking pin and hinge lever 93 arereleased and move along with the panel 90 when the panel is free to moveto its open position when the adjacent module is removed. As previouslydescribed, the panel 90 is spring loaded by torsion spring 95 to move toits open position. In one embodiment, the opening of the panel 90 may beautomated with the action of the servo motor 100 such that the panel isresting against an adjacent module when unlocked, opening fully when themodule 16 is removed. The spring lever 97 may return to its springbiased position after the locking pin 98 is released.

The servo motor 100 may be activated as soon as the OIR button 19 a onthe module to be replaced is pressed (FIGS. 2 and 9) or when the coolingstate has been reached. As described above, activation of the OIR button19 a on the OIR module may initiate powering down of the module so thatit can be extracted from the system. This may also trigger softwarecontrols (panel logic 18 b), and a signal may be transmitted to theservo motor 100 of the adjacent module to activate its panel 90. Thepanel logic 18 b may receive input from the OIR button 19 a, coolinglogic 18 b, thermal sensor 18 c, software logic that monitors modulepresence, or any combination thereof to initiate unlocking of the panel90. For example, the panel 90 may be unlocked when the OIR button 19 ais pushed, when the thermal sensor 18 c (or cooling logic 18 a)indicates that the cooling state has been reached, or based on inputfrom both the OIR button and thermal sensor. The panel logic 18 b maysend a signal to the servo motor 100 via a PCB (Printed Circuit Board)connection 101 attached to the PCB of the module 91.

The panel 90 is pushed back into its locked position when the adjacentmodule 16 is inserted back into the open slot 22 (FIGS. 2 and 9). Thelocation and length of the hinge lever 93, slotted bracket 96, andspring lever 97 are preferably optimized so that movement of the panel90 by adjacent module 16 locks the pin 98 with the panel returning toits closed (locked) position.

FIG. 10 illustrates another example of an automated mechanism foropening the panel 90 in which a shape memory alloy filament 102 is usedto move the spring lever 97 and release the locking pin 98 from itslocked position. Filament 102 is connected substantially rigidly at oneend to bracket 104 and at the other end to the spring lever 97. Filament102 operates between an elongated and a shortened state. Heatingfilament 102 to a specific phase transition temperature will initiatethe elongated to shortened phase state change. The original (shortened)shape of the shape memory alloy filament 102 is shown in a cut-out view.The filament 102 returns to its shortened state shape when it is heatedby a current pulse (typically 2-3 seconds in duration) that is passedthrough the wire 102 via PCB connection 106. As the filament 102 isshortened, it pulls lever 97, which releases pin 98 and hinge lever 93.After the current pulse ceases, filament 102 cools and spring lever 97through torsion spring 99 stretches filament 102 back to its elongatedphase state. Filament 102 may be formed from any suitable shape memoryalloy (e.g., Nitinol (nickel titanium) or any other shape memory alloy(smart metal, memory metal alloy, smart alloy)).

Additionally, filament 102 may also provide a thermo-mechanical “backup”protection feature where by setting a suitable metallurgical phasetransition temperature filament 102 may be caused to pull lever 97 iflocal system operating temperature reaches a predetermined temperaturepoint, typically within the waiting period shown in FIG. 12. Asdescribed above with the respect to the servo motor 100 of FIG. 9, thespring 102 may be activated (current applied) when the OIR button 19 ais pushed or when the cooling state has been reached.

It is to be understood that the mechanisms for unlocking the panel 90shown in FIGS. 9 and 10 are only examples and that other manual orautomated mechanisms may be used to unlock the panel without departingfrom the scope of the embodiments.

The following describes results of experiments showing the thermalimpact on the impacted module when the OIR module is removed. Without awaiting period or airflow panel 20 deployed, the temperature on theimpacted module (FC6-S2 card in the example of FIG. 2) starts toincrease as soon as the OIR module (FC2-S2 card) is removed from thesystem as air starts to bypass from the slot opening to ambient. Sinceeach module has a limit on the maximum operating temperature, thiscontinuous increase in temperature would limit the time for modulereplacement.

FIG. 11 shows a graph 111 illustrating an example of temperature rise atthe impacted module upon removal of a module without a cooling (waiting)period. Temperature is graphed over time and shows the rise intemperature when the module is removed. The temperature at the impactedmodule before removal of the OIR module is 80° C. In this example, themaximum allowed device temperature is 110° C. and the available OIR timewithout a waiting period is 235 seconds.

FIG. 12 shows a graph 112 illustrating the temperature rise after acooling (waiting) period in which the fan speed is increased before themodule is removed. As described above, the waiting period is the timeneeded to stabilize a device operating temperature to its lowest valueby increasing the fan speed (e.g., to 100%). In the example shown inFIG. 12, the OIR button is activated at Time=100 seconds. The fan speedis increased from 5400 rpm to 11000 rpm. After 120 seconds thetemperature stabilizes at its lowest point. The module is then removed(at Time=220 seconds). In this example, the available OIR time with thewaiting period is 320 seconds.

FIG. 13 shows a graph 113 illustrating an example of temperature changesover time with the airflow panel 20 deployed into open slot 22 (FIGS. 2and 13). The impacted device temperature is at steady state until themodule is removed at Time=230 seconds. The change in temperature overtime is shown with no panel and the fan speed at 5400 rpm, with no paneland the fan speed at 11000 rpm, and with the panel deployed and fanspeed at 5400 rpm. Without the panel, the temperature on the impactedmodule starts to increase as soon as the OIR module is removed from thesystem as the air starts to bypass from the slot opening to ambient.With the panel 20 deployed, the temperature at the impacted moduleimproves due to the fact that the top row slot air resistance improvedfrom the absence of the module and the closed slot opening preventedairflow bypass. The OIR time limit improved indefinitely with theairflow panel 20 deployed.

As can be observed from the foregoing, the embodiments described hereinmay provide numerous advantages. For example, one or more embodimentsallow more time for module replacement and allow for replacement timesbeyond conventional OIR times. In one or more embodiments, the airflowpanel avoids air bypass through the slot opening of the removed module,thereby improving thermal management of the system. In one or moreembodiments, cooling logic helps to maintain cooling within the modularelectronic system by pre-cooling adjacent modules before removal of theOIR module.

Although the method and apparatus have been described in accordance withthe embodiments shown, one of ordinary skill in the art will readilyrecognize that there could be variations made to the embodiments withoutdeparting from the scope of the invention. Accordingly, it is intendedthat all matter contained in the above description and shown in theaccompanying drawings shall be interpreted as illustrative and not in alimiting sense.

1: A method comprising: receiving an indication at a modular electronicsystem of initiation of online removal for a module removably insertedinto a slot of the modular electronic system; increasing a fan speed atthe modular electronic system before the module is removed; monitoringan internal temperature at the modular electronic system; and providingan indication that the module is ready for removal upon reaching aspecified cooling state at the modular electronic system based on saidtemperature monitoring; wherein a panel on an adjacent module is openedand extends into the slot upon removal of the module to substantiallyblock airflow bypass from the slot and maintain cooling within themodular electronic system. 2: The method of claim 1 wherein receivingsaid indication of initiation of the online removal comprisesidentifying a depressed Online Insertion and Removal (OIR) button at themodule. 3: The method of claim 1 further comprising unlocking the modulefor removal upon reaching said cooling state. 4: The method of claim 1wherein monitoring said internal temperature comprises monitoring athermal sensor located in an area of one of a plurality of modulesinstalled in the modular electronic system. 5: The method of claim 1further comprising turning on an indicator light at the module uponreceiving said indication of initiation of the online removal process.6: The method of claim 5 wherein providing said indication that themodule is ready for removal comprises changing the light when themodular electronic system reaches said cooling state. 7: The method ofclaim 1 further comprising unlocking the panel when said cooling stateis reached. 8: The method of claim 1 further comprising transmitting anelectrical signal to a locking mechanism to unlock the panel on theadjacent module before the module is removed. 9: The method of claim 8wherein the locking mechanism comprises a servo controlled motor. 10:The method of claim 8 wherein the locking mechanism comprises a shapememory filament. 11: An apparatus comprising: a frame supporting aplurality of slidably removable modules, at least a portion of themodules each comprising a panel movable between a closed position and anopen position in which the panel extends into an open slot from which amodule is removed; a cooling fan for cooling said modules; a thermalsensor for sensing an internal temperature at the apparatus; and aprocessor configured to receive an indication of an online removalprocess for the module, increase a speed of the cooling fan, and providean indication that the module is ready for removal upon identifying thatthe internal temperature has reached a cooling state; wherein the panelon an adjacent module is configured to open and extend into the openslot upon removal of the module to substantially block airflow bypassfrom the slot and maintain cooling within the modular electronic system.12: The apparatus of claim 11 wherein the processor is further operableto unlock the module for removal when the temperature has reached saidcooling state. 13: The apparatus of claim 11 wherein the modulecomprises an indicator light configured to indicate when said coolingstate has been reached and the module is ready for removal. 14: Theapparatus of claim 11 wherein the processor is further operable totransmit an electrical signal to a locking mechanism to unlock the panelwhen said cooling state is reached. 15: The apparatus of claim 11further comprising an electromechanical mechanism for unlocking thepanel prior to removal of the module. 16: The apparatus of claim 15wherein the electromechanical mechanism comprises a metallurgical phasetransition temperature filament configured to unlock the panel when anoperating temperature reaches a predetermined threshold. 17: Logicencoded on one or more non-transitory computer readable media forexecution and when executed by a processor operable to: identifyinitiation of an online removal process for a module removably insertedinto a slot of a modular electronic system; increase a fan speed at themodular electronic system before the module is removed; monitor aninternal temperature at the modular electronic system; provide anindication that the module is ready for removal upon reaching aspecified cooling state at the modular electronic system based on saidmonitored temperature; and unlock a panel on an adjacent module so thatthe panel is free to open and extend into the slot upon removal of themodule to substantially block airflow bypass from the slot and maintaincooling within the modular electronic system. 18: The logic of claim 17further operable to unlock the module for removal from the modularelectronic system when said cooling state is reached. 19: The logic ofclaim 17 wherein said indication comprises a visible indication. 20: Thelogic of claim 19 wherein said visible indication comprises a light atthe module.